Thermodynamics of Hierarchical Aggregation in Pigment Dispersions
Thermodynamics of Hierarchical Aggregation in Pigment Dispersions
复制标题
颜料分散体中分级聚集的热力学
DOI：
10.1021/acs.langmuir.9b02192
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发表时间：
2019
期刊：
影响因子：
3.9
通讯作者：
Jiang, Hanqiu
中科院分区：
文献类型：
--
作者：
Rishi, Kabir;Mulderig, Andrew;Beaucage, Gregory;Vogtt, Karsten;Jiang, Hanqiu
许多商业和工业上重要的材料聚集形成纳米级质量分形结构。与诸如气相二氧化硅之类的硬聚集体不同，水性颜料基油墨由表面活性剂稳定的弱结合纳米颗粒组成。这些软团聚体可以很容易地破裂和重新形成平衡的混合能量和表面能的减少与聚类或聚集。小元素晶体的快速热运动导致密集的团簇或初级颗粒。较大的初级颗粒具有较慢的热运动，并聚集成分枝质量分形，形成双层层次结构。提出了层次结构依赖于不同层次结构之间微妙的竞争平衡。采用了Vogtt的一种新的分层热力学模型。采用颜料黄14和颜料蓝15:3作为表面活性剂稳定的水分散体，探讨了纳米粒子层次平衡的热力学。结果表明，纳米粒子的可逆聚集可以用分离自由能的变化和混合自由能的变化来描述。分层热力学主要受分散性表面活性剂的溶解度影响。在表面活性剂的云点处，初级颗粒接近基本颗粒的大小，聚集程度变得非常大。结果表明，通过热平衡、操纵表面活性剂性质和元素晶粒大小，可以对颜料的层次结构和尺寸进行精细和可重复的控制。
Many commercially and industrially important materials aggregate to form nanoscale mass-fractal structures. Unlike hard aggregates such as fumed silica, aqueous pigment-based inks consist of weakly bound nanoparticles stabilized by a surfactant. These soft aggregates can easily break apart and re-form balancing mixing energy and the reduction in surface energy with clustering or aggregation. Rapid thermal motion of small elemental crystallites leads to dense clusters or primary particles. The larger primary particles have slower thermal motion and aggregate into ramified mass fractals to form a dual-level hierarchical structure. It is proposed that the hierarchical structure relies on subtle and competitive equilibria between the different hierarchical structural levels. A new hierarchical thermodynamics model by Vogtt is used. Pigment yellow 14 and pigment blue 15:3 as surfactant-stabilized aqueous dispersions were employed to explore the thermodynamics of nanoparticle hierarchical equilibria. It was demonstrated that reversible nanoparticle aggregation can be described solely by the change in free energy of dissociation and the change in free energy of mixing in the context of a subunit being removed from a cluster. The hierarchical thermodynamics is dominated by the solubility of the dispersing surfactant. At the cloud point for the surfactant, primary particles approach the size of an elemental particle and the degree of aggregation becomes very large. The results indicate that subtle and reproducible control over pigment hierarchical structure and size is possible through thermal equilibration, manipulation of the surfactant properties, and elemental crystallite size.